The online travel agencies (OTAs) had gross bookings exceeding $150 billion in 2013, representing 38% of the global online market and 13% of the global travel market. The online travel sales figure is estimated to be growing at 12% annually. OTAs have 15% of total hotel sales in the U.S. with around $19 billion of gross bookings and are expected to grow 5-6% over the next two years. OTAs customer segments span across business, leisure, and group. OLT websites play multiple roles, acting as marketing engines, booking engines, and search engines, as well as existing as an execution platform for customers. The global leaders in this space clude: Priceline and Expedia, which individually sell more than 22 million and 12 million hotel room nights per month, respectively. The world’s largest travel review platform, TripAdvisor receives 315 million monthly unique visitors, on its website. This article discusses three companies - Amazon, Alibaba and TripAdvisor - who are gearing up to provide competition to the existing leaders in the coming months. Get the full story at Trefis